Compressive Strength of Concrete -Test procedure IS-516

Compressive Strength of Concrete

This examination provides us with an understanding of the various attributes of concrete. By utilizing this assessment, we can verify whether the process of concreting has been executed correctly or not. Compressive strength refers to the capacity of a material or structure to bear the imposed loads on its surface without experiencing any fractures or deformations. When subjected to compression, a material tends to decrease in size, whereas tension causes elongation.

Compressive Strength Definition

The compressive strength of a material or structure refers to its capacity to withstand loads on its surface without experiencing any cracks or deformations. When subjected to compression, a material tends to decrease in size, whereas under tension, it elongates.

Key Takeaways

  1. The evaluation of construction project quality and safety is conducted through concrete cube testing, which includes mixing, molding, curing, and analyzing compressive strength using a precise formula for reliable outcomes.
  2. Concrete cube testing is a crucial method for assessing the quality and safety of construction projects, involving a series of steps such as mixing, molding, curing, and evaluating compressive strength through a specific formula to achieve precise results.
  3. Certified test houses play a vital role in ensuring the successful execution of projects.

The Purpose of Concrete Cube Testing

The primary objective of conducting concrete cube tests is to determine the compressive strength of the solidified concrete mixture, thereby verifying its compliance with specified standards and preventing structural problems. Ensuring the quality of concrete is vital in order to avoid issues such as cracking, crumbling, or collapsing. Apart from conducting concrete cube tests, a slump test can also be carried out to evaluate the workability of fresh concrete.

Concrete cube testing is a standard practice in the construction of commercial and industrial buildings to ensure the quality and safety of the concrete used. Neglecting to test concrete cubes can have severe consequences, underscoring the importance of verifying the quality of the final solidified concrete. Conducting tests in a timely manner is crucial for identifying any potential issues early on, enabling necessary adjustments to be made during the construction phase.

Cube Mould Size

 150mm * 150 mm * 150 mm Standard cubes are used

Equipment Required for Cube Test

* Cube moulds  ( 150mm* 150mm* 150mm )

* A tamping rod 

* A trowel

* A compressive strength testing machine ( Latest Calibration Machine )

Procedure of Test

1. Thoroughly clean the mounds and apply oil inside the cube frame.

2. Fill the molds with concrete in layers approximately 50mm thick.

3. Compact each layer with a tamping rod (steel bar 16mm diameter and 600 mm long) using not less than 35 strokes per layer.

4. Top Level of the Cube Mould surface smoothenby using trowel.

5 . The concrete cubes are typically removed from the molds between 16 to 72 hours, usually after 24 hours. 

6. Remove the specimen from water after the specified curing time, wipe out excess water from the surface, and measure the dimensions of the specimen to the nearest 0.2mm. 

7. Place the specimen in the machine so that the load is applied to the opposite sides of the cube cast. 

8. Align the specimen centrally on the base plate of the machine and gently rotate the movable portion by hand until it touches the top surface of the specimen. 

9. Apply the load gradually, without shock, and continuously at a rate of 140 kg/cm2/min until the specimen fails.

10.  Record the maximum load and make a note of it.

Frequency For Casting Cube Moulds

Quantity of Concrete (in m3) Number of samples ( NO’s )
0-5 m36
6-15 m39
16-30 m312
31-50 m315
51-100 m318
101-150 m321
151-200 m324

Calculations for Compressive Strength

Size of the cube =150mm x 150mm x 150mm

Area of the specimen =22500 m2

Noted load from machine =……….tones = ………….N

Compressive strength = (Load in N/ Area in mm2)=…………N/mm2

Example :-

If The Machine Reading Is 725 KN

 Compressive strength = ----------------  = 32.22 N/mm2

Testing the Compressive Strength

After undergoing the appropriate curing process, the concrete cubes are prepared for testing their compressive strength, guaranteeing that they satisfy the minimum requirements for concrete compressive strength. The procedure encompasses the subsequent stages:

* The cured cube is placed in a compressive strength testing machine.

* A force is applied until it breaks.

* The rate at which it crushes is recorded.

* This value serves as its compressive strength.

What are the Factors Affecting Concrete Cube Test Results

* Specimen size

* Shape

* Friction at the ends

* Physical and mechanical properties of the aggregate


Format Book

Compressive Strength of Concrete

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